Extraction of water particles from atmospheric air through a Scheffler reflector using different solid desiccants

ABSTRACT

In this article, an attempt has been made to extract water particles from atmospheric air by using silica gel, molecular sieve13× and activated alumina. The cycle consists of two phases, first is a nocturnal phase (night) and other is a diurnal phase (day time). In the nocturnal phase, adsorption process takes place, regeneration and condensation processes take place in the diurnal phase. The water production rate depends upon the regeneration rate of the material. A newly designed fixed focus Scheffler reflector of surface area 1.54?m² is used to regenerate the desiccant materials. The water produced from this method is clean and can be used for potable purposes. The production rate of water is 43, 38 and 155?ml/day from 1?kg each of the molecular sieve, activated alumina and silica gel, respectively; furthermore, the adsorption rate, regeneration rate and cost analysis are also carried out.     

Indoor air quality audit implementation in a hotel building in Portugal

Hotels are designed to provide high levels of comfort for guests; however, frequent complaints related to uncomfortable thermal environment and inadequate indoor air quality (IAQ) appear. On the other hand, there is little research concerning IAQ audits of hotels up to now.     

Heat transfer enhancement of the latent heat storage system using different encapsulating materials with and without fins

This study is aimed at analysing the heat transfer characteristics of different encapsulating materials and the fins on the overall heat transfer in the latent heat storage system (LHSS). Experimentation is done with different phase change materials (PCMs) (d-mannitol, d-sorbitol and paraffin wax) using different encapsulating materials, i.e. copper, aluminium and brass, with and without fins. During the charging process, there is an average 15% heat loss of copper encapsulations without using fins as compared with using fins. The heat losses in aluminium and brass encapsulations are 10% and 15%, respectively. In the discharging process, 23% of heat extraction loss is seen in copper encapsulations, 5% and 18% in aluminium and brass encapsulations, respectively. The results showed that the usage of fins is an effective technique to increase the heat stored and recovered in a LHSS. The most cost-effective encapsulation is aluminium balls with fins as it has the lowest cost/kJ as compared with other two.     

Investigating synergism during sequential inactivation of MS-2 phage and Bacillus subtilis spores with UV/H2O2 followed by free chlorine

A sequential application of UV as a primary disinfectant with and without H₂O₂ addition followed by free chlorine as secondary, residual disinfectant was performed to evaluate the synergistic inactivation of selected indicator microorganisms, MS-2 bacteriophage and Bacillus subtilis spores. No synergism was observed when the UV irradiation treatment was followed by free chlorine, i.e., the overall level of inactivation was the same as the sum of the inactivation levels achieved by each disinfection step. With the addition of H₂O₂ in the primary UV disinfection step, however, enhanced microbial inactivation was observed. The synergism was observed in two folds manners: (1) additional inactivation achieved by hydroxyl radicals generated from the photolysis of H₂O₂ in the primary UV disinfection step, and (2) damage to microorganisms in the primary step which facilitated the subsequent chlorine inactivation. Addition of H₂O₂ in the primary disinfection step was also found to be beneficial for the degradation of selected model organic pollutants including bisphenol-A (endocrine disruptor), geosmin (taste and odor causing compound) and 2,4-D (herbicide). The results suggest that the efficiency of UV/free chlorine sequential disinfection processes, which are widely employed in drinking water treatment, could be significantly enhanced by adding H₂O₂ in the primary step and hence converting the UV process to an advanced oxidation process.     

The fate of chlorine in recirculating cooling towers Field results

Chlorine and chloramines are volatile compounds which are stripped (“flashed off”) from recirculating cooling water systems by the large volumes of air which flow through the water in the cooling tower. The fraction of a volatile gas, such as hypochlorous acid (HOCl), which is removed by stripping is determined by Henry's constant H for that gas: H = X_G/X_L, where X_G is the mole fraction of the gas in the air and X_L is the mole fraction of the gas in the water. We have measured H for HOCl, OCl⁻, NH₃, NH₂Cl, NHCl₂ and NCl₃ at 20 and 40°C. We found H = 0.076 for HOCl, compared to 0.71 for NH₃, at 20°C. At 40°C, H was about 2.5-fold larger for HOCl. This means that 10–15% of the HOCl is stripped from cooling water on each passage through a typical cooling tower. The measured flashoff of free available chlorine (HOCl + OCl⁻) was markedly pH-sensitive with a pK of 7.5, exactly as expected if HOCl is volatile but OCl⁻ is not. The data permit a quantitative understanding of the fate of chlorine in cooling systems. The values of H at 40°C for NH₂Cl, NHCl₂ and NCl₃ were 1.28, 3.76 and 1067. This means that all of the chloramines are quickly stripped in a cooling tower.     

Effect of moderate pre-oxidation on the removal of Microcystis aeruginosa by KMnO4-Fe(II) process: significance of the in-situ formed Fe(III)

This study developed a novel KMnO₄-Fe(II) process to remove the cells of Microcystis aeruginosa, and the mechanisms involved in have been investigated. At KMnO₄ doses of 0-10.0 μM, the KMnO₄-Fe(II) process showed 23.4-53.3% higher efficiency than the KMnO₄-Fe(III) process did. This was first attributed to the moderate pre-oxidation of M. aeruginosa by KMnO₄, achieved by dosing Fe(II) after a period of pre-oxidation, to cease the further release of intracellular organic matter (IOM) and the degradation of dissolved organic matter (DOM). The extensive exposure of M. aeruginosa to KMnO₄ in KMnO₄-Fe(III) process led to high levels and insufficient molecular weight of DOM, inhibiting the subsequent Fe(III) coagulation. Additionally, Fe(II) contributed to lower levels of the in-situ formed MnO₂, the reduction product of KMnO₄ which adversely affected algae removal by Fe(III) coagulation. However, the in-situ formed Fe(III), which was derived from the oxidation of Fe(II) by KMnO₄, in-situ MnO₂, and dissolved oxygen, dominated the remarkably high efficiency of KMnO₄-Fe(II) process with respect to the removal of M. aeruginosa. On one hand, in-situ formed Fe(III) had more reactive surface area than pre-formed Fe(III). On the other hand, the continuous introduction of fresh Fe(III) coagulant showed higher efficiency than one-off dosage of coagulant to destabilize M. aeruginosa cells and to increase the flocs size. Moreover, the MnO₂ precipitated on algae cell surfaces and contributed to the formation of in-situ formed Fe(III), which may act as bridges to enhance the removal of M. aeruginosa.     

Nutrient removal from effluents by an artificial wetland: Influence of rhizosphere aeration and preferential flow studied using bromide and dye tracers

Sewerage and effluents from rural industry can be treated by percolation through the root zones of emergent macrophytes growing in a gravel substratum. The hydrology of these systems is complex, being driven by both gravity and transpiration, and so measurements of nutrient transformations within the systems are complicated by incomplete mixing. Pulse addition of dye and bromide tracers concurrently with nutrients, has been used in one such experimental artificial wetland to investigate the rates and processes of nutrient removal. The tracer was used for comparison to compensate for incomplete mixing and concentration caused by evapotranspiration. Nitrogen removal efficiency is dependent on sequential mineralization of organic nitrogen to ammonium-nitrogen, followed by nitrification of the ammonium to nitrate or nitrite and denitrification of nitrate or nitrite to gaseous nitrogen products. The effluent from a rendering plant was dominated by organic and ammonium-nitrogen, and efficiency of nitrogen removal was probably impaired by inadequate rates of mineralization and nitrification. Aeration is required for the latter process. Apparently the macrophytes were not introducing sufficient oxygen into the effluent for nitrification to be complete. This may reflect an inadequate outward radial diffusion of oxygen into the rhizosphere, or the effects of channelling of the effluent in preferential flow paths around the aerating root masses, requiring changes in system design.     

Integration of distributed generation systems into generic types of commercial buildings in California

Distributed generation (DG) of combined cooling, heat, and power (CCHP) has been gaining momentum in recent years as an efficient, secure alternative for meeting increasing power demands in the world. One of the most critical and emerging markets for DG-CCHP systems is commercial and institutional buildings. The present study focuses analysis on the main economic, energy-efficiency, and environmental impacts of the integration of three types of advanced DG technologies (high-temperature fuel cells, micro-turbines, and photovoltaic solar panels) into four types of representative generic commercial building templates (small office building, medium office building, hospital, and college/school) in southern California (e.g., mild climate), using eQUEST as energy simulation tool. Detailed load profiles for the four commercial building types during times of peak electric and peak gas consumption were analyzed and complementary strategies to further increase overall building energy efficiencies such as energy efficiency measures (e.g., day lighting, exterior shading, improved HVAC performance) and thermally activated absorption cooling were also investigated. Results show that the high-temperature fuel cell (HTFC) performance is best matched with the hospital energy loads, resulting in a 98% DG capacity factor, 85% DG heat recovery factor, and $860,000 in energy savings (6 years payback). The introduction of thermally driven double-effect absorption cooling (AC) in the college building with HTFC reduces significantly the building electricity-to-thermal load ratio and boosts the heat recovery factor from 37% to 97%.     

Role of cell surface components on Cu2+ adsorption by Pseudomonas putida 5-x isolated from electroplating effluent

A gram-negative bacterium Pseudomonas putida 5-x with high Cu2+ accumulating capability was isolated from electroplating effluent in Kwun Tong, Hong Kong. The pretreated cells without superficial layer-capsule, isolated cell envelopes and the separated peptidoglycan layer materials were obtained from fresh P. putida 5-x cells, their Cu2+ adsorption capacities and properties were compared with that of the fresh cells. Pretreatment by 0.1 mol L(-1) HCl enhanced Cu2+ adsorption capacity due to the degradation of cell superficial layer-capsule of P. putida 5-x cells. Isolated cell envelopes possessed five times more Cu2+ adsorption capacity than that of fresh intact cell. The Cu2+ adsorption of separated peptidoglycan layer materials indicated that the peptidoglycan layer only played 10-15% part of the Cu2+ adsorption capacity, and implied other cell surface components such as outer membrane or inner membrane might play an important role in such high Cu2+ binding of the cell envelopes. The adsorption process of fresh cells, pretreated cells and cell envelopes of P. putida 5-x could be described with Freundlich isotherm, while the adsorption of Cu2+ by separated peptidoglycan layer materials was better described with Langmuir isotherm.     

Pharmaceuticals, personal care products and endocrine-disrupting chemicals in U.S. surface and finished drinking waters: A proposed ranking system

This study developed a comprehensive ranking system, for the first time as per authors' knowledge, for prioritizing the monitoring of pharmaceuticals and personal care products and endocrine-disrupting chemicals (together termed as EOCs, hereafter; a total of 100 EOCs considered) in U.S. stream water/source water and finished drinking water (termed as “EOCRank,” hereafter). The EOCRank system was developed using a total of 4 criteria: (1) occurrence, (2) treatment in drinking water treatment plants, (3) ecological effects, and (4) health effects and characterized using 7 attributes: prevalence, frequency of detection, removal, bioaccumulation, ecotoxicity (for fish, daphnid, and algae aquatic indicator species), pregnancy effects, and health effects. The health effects attribute was characterized using 7 sub-attributes: carcinogenicity, mutagenicity, impairment of fertility, central nervous system acting, endocrine effects, immunotoxicity, and developmental effects. Rank scores of EOCs were calculated as summations of multiplications of importance weights and utility functions of multiple criteria and were arranged to highlight EOCs needing immediate attention. Two different ranking lists of EOCs were developed for U.S. finished drinking water and stream water/source water and observed to differ with each other, indicating the effect of water type on ranking of EOCs. A ranking list of priority EOCs, developed using a particular criterion, was observed to differ with that, developed using multiple criteria. Health effects and treatment criteria were observed to be important criteria influencing overall data gap rank scores and need further data collection. The generalized nature of the system could be customized for specific geographical locations (occurrence information and importance weights of different components). The developed database of the EOCRank system is available on: http://www.egr.msu.edu/~xagorara/research.html).